Electric hand power tool

ABSTRACT

An electric hand power tool has a machine, an air-cooled electric motor which is accommodated in the housing, a tool which is driven by the electric motor, a handle and an auxiliary handle for a two-hand guidance of the power tool, the auxiliary handle being hollow and formed as an air channel for spent air leaving the electric motor.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to an electric hand power tool.

[0002] In electric hand power tools, air required for cooling of anelectric motor is aspirated by an air impeller, which is fixedlyarranged on the driven shaft of the electric motor, through an inletslot in the power tool housing and blown through outlet slots into thepowertool housing. Air which is supplied by the air vanes of theimpeller wheel flows on the outlet edges of the outlet slots with highspeed, resulting in intense noise generation in an unpleasant highfrequency region.

SUMMARY OF THE INVENTION

[0003] Accordingly, it is an object of the present invention to providean electric hand power tool of the above mentioned general type, whichavoids the disadvantages of the prior art.

[0004] In keeping with these objects and with others which will becomeapparent hereinafter, one feature of the present invention resides,briefly stated, in an electric hand power tool which has a housing; anair-cooled electric motor which is accommodated in said housing; a toolwhich is driven by said electric motor; a handle and an auxiliary handlefor a two-hand guidance of the machine, said auxiliary handle beinghollow and used as an air channel for spent air leaving said electricmotor.

[0005] When the electric hand power tool is designed in accordance withthe present invention, it has the advantage that by the withdrawal ofthe spent air which leaves the electric motor through the hollowauxiliary handle, on the one hand the air noise is dampened inparticular the unpleasant high frequency region is lowered, and on theother hand the spent air is supplied outside away from the operator, sothat it does not blow on the operator during the operation of themachine.

[0006] In accordance with a preferable embodiment of the invention, theair passage is formed in the housing and provided with an air inletopening for the motor spent air, which opens into the inlet of theauxiliary handle. With this closed air passage, the path between theimpeller vanes of the motor impeller sitting on the motor shaft and theinlet of the auxiliary handle is bridged and thereby a good damping ofthe flow noise is obtained.

[0007] In accordance with a preferable embodiment of the presentinvention, the air passage is formed screw-shaped or spiral-againstshaped with an inner diameter which continually increases toward theinlet of the hollow auxiliary handle. Thereby the channel operates as anunloading space, whereby a high air quantity with a reduced flow speedcan be transported for additionally significantly reducing the noisegeneration. The screw-shaped construction is advantageous for the case,in which the rotary direction of the electric motor and thereby of themotor impeller is opposite to the rotary direction of the tool.

[0008] In accordance with a further embodiment of the invention, theauxiliary handle or an outlet pipe which surrounds an outlet of theauxiliary handle is formed turnable. Thereby the outflow of the motorspent air is adjusted so that it can not flow unpleasantly to theoperator in any work application. With the auxiliary handle which isturnable and arrestable in the adjusted turning position, it is possibleto provide an individual optimization of the ergonomics of the powertool by adaptation to individual gripping habits of the operator.

[0009] In accordance with a preferable embodiment of the presentinvention, the hollow auxiliary handle is formed as a bracket handle,which in the electric hand power tool with a rotatable tool at leastpartially covered by a protective hood, is placed with one handle end onthe protective hood, while at or near its another end it is fixed on ahousing part of the housing which accommodates the electric motor, andits inlet is located under the protective hood. Thereby a solidmechanical connection of the auxiliary handle with the housing isprovided and because of the immanently great handle region of a brackethandle, a reliable handling of the power tool both for a left-handed andright-handed person is possible, which provides also a flexible handleposition in different work applications.

[0010] The novel features which are considered as characteristic for thepresent invention are set forth in particular in the appended claims.The invention itself, however, both as to its construction and itsmethod of operation, together with additional objects and advantagesthereof, will be best understood from the following description ofspecific embodiments when read in connection with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a view showing an electric hand circular power saw inaccordance with the present invention;

[0012]FIG. 2 is a plan view of the electric hand circular power saw ofFIG. 1 without a support plate;

[0013]FIG. 3 is a side view of the electric hand circular power saw ofFIG. 2 after a removal of the protective hood and a circular saw blade;

[0014]FIG. 4 is a side view of the electric hand power tool of FIG. 1with a removed protective hood for a circular saw blade.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] An electric hand circular power saw is shown in the drawings asan example for an electric hand power tool for chip-removing or grindingtreatment of workpieces. It has a two-shell housing 10 with a handle 11formed on it for guiding and handling of the power tool and with a motorhousing 12 placed on it and accommodating an air-cool electric motor.

[0016] The electric motor drives a drive shaft 13 through a not shownone-stage transmission, and a saw blade 14 is mounted on the driveshaft. The circular saw blade 14 is covered in an upper region by aprotective hood 15 which is screwed to the housing 10. The protectivehood 15 extends to a support plate 16 which is connected with themachine housing 10. The support plate 16 is used for placing the powertool on the workpiece during a sawing process. The circular saw blade 14extends through the support plate 16 and projects beyond it, downwardlymore or less depending on a desired cutting depth.

[0017] For adjustment of the cutting depth to the machine, the supportplate 16 is turnable about a turning axle which is fixed on the machinehousing 10 forwardly on the circular saw blade 14 as seen in a workingdirection. The selected turning position is fixed by an adjustingdevice. A second adjusting device 17 is arranged on the support plate18, and by turning the support plate 16 around a longitudinal axisextending parallel to the saw blade plane, enables a cutting angleadjustment of the power tool.

[0018] For providing a two-hand guidance of the powertool for sawing,the power tool has an auxiliary handle 21. It is formed as a brackethandle and arranged forwardly of the drive shaft 13 of the circular sawblade 14 as considered in the working direction of the power tool, nearits front region on the machine housing 10. The auxiliary handle whichis identified herein below as the bracket handle 21. Its one handle endis placed on the protective hood 15. Its gripping region 211 which issubstantially parallel to the rotary axis of the circular saw blade 14,extends above the support plate 16 at a distance from it. Its anothergripping end is fixed on the motor housing 12. Thereby a very solidmechanical connection of the bracket handle 21 on the machine housing 10is guaranteed.

[0019] By means of the auxiliary handle 21, the power tool can be placedvery accurately planely on the workpiece, and during sawing can be heldand guided very well with two hands. The great gripping region of thebracket handle 21 provides an ergonomic and reliable handling of thepower tool in all work applications, both for a right-handed and aleft-handed person. Moreover, it is possible to support the power toolwith the bracket handle 21 in its center of gravity.

[0020] The bracket handle 21 is hollow and has an inlet 22 which is opento the interior of the protective hood 15 as shown in FIGS. 3 and 4. Italso has an outlet 23 arranged behind the handle region 211 as shown inFIGS. 1 and 2. Preferably the outlet 23 is located at or near the end ofthe bracket handle 21 which faces away from the inlet 22. The outlet 23is closed by an outlet pipe 24 which can be formed preferably turnable.For the air cooling of the electric motor, the motor housing 12 has airinlet slots 25 shown in FIG. 25. Air which is aspirated by a not shownair impeller connected for rotation with the driven shaft of theelectric motor is aspirated through the air inlet slots. The air whichis aspirated by the air impeller passes through the electric motor andis blown out as a heat-withdrawing motor spent air, and it is guided sothat it flows into the inlet 22 of the hollow bracket handle 21. Forthis purpose an air passage 26 is formed in the housing 10. It expandstoward the inlet 22 of the bracket handle 21 and opens into the inlet 22as shown in FIG. 3.

[0021] The air is blown by the air impeller from the interior of theelectric motor into an air inlet opening of the air passage 26 which iscovered in FIG. 3. The motor spent air flows, as shown by the arrow 27in FIG. 3, through the air passage 26 of the hollow bracket handle 21,and is discharged through the outlet 23 which is formed in the brackethandle 21 and surrounded by the outlet pipe 24. The outlet pipe 24 isoriented so that the flow direction of the motor spent air flowing outhere is oriented away from the operator of the power tool. When theoutlet pipe 24 is turnably movable, the operator can individually adjustthe air discharge device as convenient to him or as necessary for thework applications.

[0022] Since as mentioned herein above, a one-stage transmission isarranged between the electric motor and the drive shaft 13 of thecircular saw blade 14, the rotary directions of the rotor of theelectric motor and the circular saw blade 14 are inverted. The rotarydirection of the circular saw blade 14 is identified in FIG. 4 by thearrow 28. For supplying the motor spent air which leaves the electricmotor to enhance the flow through the air passage 26 into the brackethandle 21, the air passage 26 is closed and formed screw-shaped, as canbe seen partially in FIG. 3. It extends from its air inlet opening tothe inlet 22 of the bracket handle 21 as an axially expanding spiral,wherein the throughgoing diameter of the air passage 26 is preferablycontinuously increased.

[0023] The two-shell housing 10 is injection molded of syntheticplastic. At least the handle 11 and the air passage 22 are moldedtogether in the same way. The bracket handle 21 is formed as an insertpart, but in certain circumstances can be also molded. The screw-shapedair passage 26 which expands toward the inlet 22 of the bracket handle21 is molded on parts in both shells, so as to complete the air passage26 when the shells are assembled with one another.

[0024] In accordance with a modification of the above described electrichand circular power tool, the bracket handle 21 is formed turnablearound its inlet 22 and is arrestable in any of adjusted turningpositions. Thereby, in addition to the possibility of adjusting thenoise radiating direction, also an ergonomic effect is obtained.

[0025] The invention is not limited to the specific electric handcircular power saw. It can be used for all hand-guided electric powertools with rotatable tools such as for example masonry mills? rock saws,angle grinders, concrete grinders, eccentric grinders, etc.

[0026] It will be understood that each of the elements described above,or two or more together, may also find a useful application in othertypes of constructions differing from the types described above.

[0027] While the invention has been illustrated and described asembodied in electric hand power tool, it is not intended to be limitedto the details shown, since various modifications and structural changesmay be made without departing in any way from the spirit of the presentinvention.

[0028] Without further analysis, the foregoing will so fully reveal thegist of the present invention that others can, by applying currentknowledge, readily adapt it for various applications without omittingfeatures that, from the standpoint of prior art, fairly constituteessential characteristics of the generic or specific aspects of thisinvention.

What is claimed as new and desired to be protected by letters patent isset forth in the appended claims.
 1. An electric hand power tool,comprising a housing; an air-cooled electric motor which is accommodatedin said housing; a tool which is driven by said electric motor; a handleand an auxiliary handle for a two-hand guidance of the power tool, saidauxiliary handle being hollow and formed as an air channel for spent airleaving said electric motor.
 2. An electric hand power tool as definedin claim 1, wherein said auxiliary handle is turnable between aplurality of turning positions and arrestable in at least one of saidturning positions.
 3. An electric hand power tool as defined in claim 1,wherein said auxiliary handle has an outlet formed at a handle end whichis remote from said housing and an outlet which is open toward saidhousing, arranged so that the spent air flows into said inlet of saidauxiliary handle.
 4. An electric hand power tool as defined in claim 3;and further comprising an outlet pipe which surrounds said outlet.
 5. Anelectric hand power tool as defined in claim 4, wherein said outlet pipeis formed turnable.
 6. An electric hand power tool as defined in claim1; and further comprising an air passage formed in said housing andhaving an air inlet opening provided for the spent air of said electricmotor and opening into said inlet of said auxiliary handle.
 7. Anelectric hand power tool as defined in claim 6, wherein said air passageexpands toward said inlet of said auxiliary handle.
 8. An electric handpower tool as defined in claim 6, wherein said air passage which guidesthe spent air of the electric motor is screw-shaped when rotarydirections of said electric motor and said rotatable tool are inverted.9. An electric hand power tool as defined in claim 7, wherein said airpassage which guides the spent air of the electric motor is screw shapedwhen rotary directions of said electric motor and said tool areinverted.
 10. An electric hand power tool as defined in claim 6; andfurther comprising a protective hood which at least partially coverssaid tool, said inlet of said auxiliary handle being arranged in saidprotective hood, and said air passage opens in said protective hooddirectly at said inlet of said auxiliary passage.
 11. An electric handpower tool as defined in claim 7; and further comprising a protectivehood which at least partially covers said tool, said inlet of saidauxiliary handle being arranged in said protective hood, and said airpassage opens in said protective hood directly at said inlet of saidauxiliary passage.
 12. An electric hand power tool as defined in claim8; and further comprising a protective hood which at least partiallycovers said tool, said inlet of said auxiliary handle being arranged insaid protective hood, and said air passage opens in said protective hooddirectly at said inlet of said auxiliary passage.
 13. An electric handpower tool as defined in claim 1; and further comprising a protectivehood which at least partially covers said tool, said hollow auxiliaryhandle being formed as a bracket handle which is placed with one handleend at said protective hood, and at or near its another handle end isfixed on a housing part of said housing which receives said electricmotor.